A plasma display, EL display device, and image display device using an electron beam are known as emissive type image display devices. In recent years, demands are arising for larger-screen, higher-resolution image display devices, and needs for emissive type image display devices are increasing.
For example, as an emissive type image display device using an electron beam, the present applicant has applied a thin image display device in which an electron source for generating an electron beam is arranged in an envelope that is made up of a face plate, rear plate, and outer frame and can maintain vacuum, surface-conduction type electron-emitting devices are arrayed in a matrix as the electron source, an electron beam emitted by the electron source is accelerated to irradiate a fluorescent substance applied to the face plate, and the fluorescent substance emits light to display an image (e.g., Japanese Patent Laid-Open Nos. 7-235255, 11-312461, 8-171849, 2000-311594, and 11-195374, EP-A-0908916).
The surface-conduction type electron-emitting device is constituted by forming on a substrate a pair of opposing electrodes, and a conductive film which is connected to the pair of electrodes and partially has a gap. A carbon film mainly consisting of at least one of carbon and a carbon compound is formed at the gap.
Such electron-emitting devices can be arrayed on a substrate and wired to each other to fabricate an electron source having a plurality of surface-conduction type electron-emitting devices.
This electron source can be combined with a fluorescent substance to form an image display device.
The electron source and image display device are manufactured as follows.
As the first manufacturing method, a plurality of units each made up of a conductive film and a pair of electrodes connected to the conductive film, and wires connected to the electrodes of the respective units are formed on a substrate. The resultant substrate is set in a vacuum chamber. After the vacuum chamber is evacuated, a voltage is applied to each unit to form a gap in the conductive film of the unit (“forming” step). A carbon compound gas is introduced into the vacuum chamber, and a voltage is applied to each unit via an external terminal in this atmosphere. By voltage application, a carbon film mainly consisting of at least one of carbon and a carbon compound is formed near the gap (“activation” step). As a result, each unit is changed into an electron-emitting device, and an electron source made up of a plurality of electron-emitting devices is obtained. After that, the substrate having the electron source, and a substrate having a fluorescent substance are joined at an interval of several mm to fabricate the panel of an image display device.
As the second manufacturing method, a plurality of units each made up of a conductive film and a pair of electrodes connected to the conductive film, and wires connected to the electrodes of the respective units are formed on a substrate. The resultant substrate, and a substrate having a fluorescent substance are joined at a small interval of several mm to fabricate the panel of an image display device. The interior of the panel is evacuated via an exhaust pipe connected to the panel, and a voltage is applied to each unit via the external terminal of the panel to form a gap in the conductive film of the unit (“forming” step). A carbon compound gas is introduced into the panel via the exhaust pipe, and a voltage is applied again to each unit via the external terminal in this atmosphere. By voltage application, a carbon film mainly consisting of at least one of carbon and a carbon compound is formed near the gap (“activation” step). Thus, each unit is changed into an electron-emitting device, and an electron source made up of a plurality of electron-emitting devices is attained.
As the first manufacturing method, a method disclosed in Japanese Patent Laid-Open No. 11-312461 will be explained.
FIG. 8 is a schematic view showing an image display device manufacturing apparatus described in this reference.
In FIG. 8, reference numeral 71 denotes a glass substrate on which a plurality of units and wires connected to the units are formed; 133, an vacuum chamber; 134, a gate valve; 135, an exhaust device; 136, a pressure gauge; 137, Q-mass as a quadruple-pole mass spectrometer; 138, a gas inlet line; 139, a gas inlet controller constituted by a solenoid valve, mass-flow controller, or the like; and 140, a supply substance source.
A plurality of units each made up of a pair of electrodes and a conductive thin film are formed on the substrate 71, and matrix wires to be connected to the units are formed (not shown).
The pair of electrodes are formed as follows. A conductive material such as a metal (Pt, Au, or the like) is formed into a film by sputtering or vapor deposition. The photolithography step including resist coating, exposure and-developing of an electrode pattern, plasma etching, and plasma ashing is performed to form electrodes.
The substrate 71 is set in the vacuum chamber 133 of the manufacturing apparatus shown in FIG. 8, and the matrix wires are electrically connected to a voltage application means outside the vacuum chamber. After the interior of the vacuum chamber 133 is evacuated, a voltage pulse is applied to each unit via the matrix wires to perform the above-mentioned “forming step”.
After the interior of the vacuum chamber 133 is sufficiently evacuated, an organic substance is supplied from the supply substance source 140 into the vacuum chamber 133 while the pressure gauge 136 and Q-mass 137 are monitored to set a desired pressure and partial pressure. Similar to the “forming” step, a voltage pulse is applied to each unit to execute the above-described “activation” step, which changes each unit into an electron-emitting device. After the “activation” step, the substrate 71 is unloaded from the vacuum chamber 133. The obtained substrate 71 serves as an electron source substrate.
The electron source substrate, a face plate having a fluorescent substance on its inner surface, and a support frame having an exhaust pipe formed from a glass pipe and getters mainly consisting of Ba are temporarily fixed via frit glass so as to oppose each other. The structure is baked in a heating furnace in an inert gas atmosphere to fabricate an airtight envelope.
An exhaust pipe is connected to the exhaust device 135 to evacuate the interior of the envelope. The exhaust pipe is chipped off by a burner or the like. The getters are flashed by RF heating to form a Ba film, and the vacuum in the envelope after chipping-off is maintained. In this fashion, an image display device formed from an envelope is fabricated.